Welcome to Australia's only Vintage Radio and Television discussion forums. You are not logged in. Please log in below, apply for an account or retrieve your password.
Australian Vintage Radio Forums
  Home  ·  About Us  ·  Discussion Forums  ·  Glossary  ·  Outside Links  ·  Policies  ·  Services Directory  ·  Safety Warnings  ·  Tutorials

Tech Talk

Forum home - Go back to Tech talk

 Airzone 457B / Malvern Star MS457B
« Back · 1 · 2 · Next »
 Return to top of page · Post #: 1 · Written at 11:33:54 AM on 24 June 2019.
STC830's Gravatar
 Location: NSW
 Member since 10 June 2010
 Member #: 681
 Postcount: 805

I am currently researching this radio of which I have the Airzone version with miniature valves, hoping someone has a schematic. An image appears on Google images:

https://www.google.com/imgres?imgurl=https%3A%2F%2Fvintage-radio.com.au%2Fphotos%2Fairzone-portable-1-141215.jpg&imgrefurl=https%3A%2F%2Fvintage-radio.com.au%2Fhome.asp...

This is supposed to link to this forum but does not as it comes up with a 404 error:

https://vintage-radio.com.au/default.asp?f=1&th=959

This radio has a leather handle whereas mine has a bakelite handle, like this Malvern Star MS457B:

https://www.radiomuseum.org/r/malvern_ms457b.html

A schematic would be much appreciated.


 
 Return to top of page · Post #: 2 · Written at 1:11:50 PM on 24 June 2019.
STC830's Gravatar
 Location: NSW
 Member since 10 June 2010
 Member #: 681
 Postcount: 805

I have realised that the Airzone model number is 457B and have edited the thread title. There is no model number on the chassis so have been going on photos from the net.

The 457B has miniature valves 1R5 1T4 1S5 3V4.


 
 Return to top of page · Post #: 3 · Written at 8:44:41 PM on 24 June 2019.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 3701

Malvern Star MS457B comes up as 1948 in AORSM's


 
 Return to top of page · Post #: 4 · Written at 8:50:18 AM on 25 June 2019.
STC830's Gravatar
 Location: NSW
 Member since 10 June 2010
 Member #: 681
 Postcount: 805

Radiomuseum says agrees. Speaker transformer says 20 May 52 suggesting that the radio was around for a while. Speaker says TEST 29J6 suggesting 46 or 56.

Re AORSM, radiomuseum has 1948 for the age of the Airzone version, but says AORSM Volume 7, 1949, Page 47

Malvern Star vesion is given as 1948, with no AORSM reference.

Peal also made a version with a timber front (https://www.radiomuseum.org/r/airzone_peal_p457b.html) and says AORSM Volume 7, 1949, Page 291.

So looks like '48 or '49 AORSM for a circuit.


 
 Return to top of page · Post #: 5 · Written at 6:15:28 PM on 25 June 2019.
Robbbert's avatar
 Location: Sydney, NSW
 Member since 18 September 2015
 Member #: 1801
 Postcount: 1074

The link to this forum should be

https://vintage-radio.com.au/home.asp?f=1&th=959


 
 Return to top of page · Post #: 6 · Written at 7:18:34 PM on 25 June 2019.
STC830's Gravatar
 Location: NSW
 Member since 10 June 2010
 Member #: 681
 Postcount: 805

Thanks for that Robbbert


 
 Return to top of page · Post #: 7 · Written at 9:55:12 PM on 25 June 2019.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 3701

Its definitely in AORSM's: I have the disk & its there under Malvern Star.


 
 Return to top of page · Post #: 8 · Written at 8:11:07 AM on 26 June 2019.
STC830's Gravatar
 Location: NSW
 Member since 10 June 2010
 Member #: 681
 Postcount: 805

Marcc, my email address is showing if you could be good enough to send it.


 
 Return to top of page · Post #: 9 · Written at 10:16:00 PM on 26 June 2019.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 3701

Found & tidied up circuit. Email is showing as hidden, therefore: Mission impossible.


 
 Return to top of page · Post #: 10 · Written at 7:08:25 AM on 27 June 2019.
STC830's Gravatar
 Location: NSW
 Member since 10 June 2010
 Member #: 681
 Postcount: 805

Sorry about that; now unhidden.


 
 Return to top of page · Post #: 11 · Written at 10:05:11 AM on 27 June 2019.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 3701

It should now be on the way.


 
 Return to top of page · Post #: 12 · Written at 2:01:11 PM on 27 June 2019.
STC830's Gravatar
 Location: NSW
 Member since 10 June 2010
 Member #: 681
 Postcount: 805

Thanks Marcc, safely arrived and printed.


 
 Return to top of page · Post #: 13 · Written at 3:25:03 PM on 28 June 2019.
STC830's Gravatar
 Location: NSW
 Member since 10 June 2010
 Member #: 681
 Postcount: 805

Have had a quick look at the radio and the valves are 1R5, ?, ?, 3S4, two having their numbers illegible. I guess that this would be 1R5, 1T4, 1S5, 3S4 as this is a combination mentioned on the net along with the combination 1R5, 1T4, 1S5, 3V4 given in the circuit that you sent.

3V4 and 3S4 have different output impedances (10k and 8k); attached components vary as well, according to the net.

Need to go through all components now to find out what else is different.

Looks like modifications have occurred from the publication of the circuit to the manufacture of this particular radio, at least 3 years, omitting the possibility of a wrong substitution of valve. The circuit looks untouched and original otherwise.


 
 Return to top of page · Post #: 14 · Written at 4:28:53 PM on 28 June 2019.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 3701

Check the wiring 3V4 & 3S4 are not pin interchangeable.

3S4 ********** 3V4

1. F-; ************* F-
2. Plate; ********** P
3.g1; ************* g2
4.g2 Sceeen; **** nc
5.fm g3 (suppressor) & filament tap;**** FM g3
6. Plate; ********** g1
7. F+; ************* F+

3S4 runs lower screen voltage 67.5 vs 90.

Franks electron tube data for valve sheets. If you get a good sharp photo of the unknowns one can often identify them by the way the innards are made

Had to add asterisks as it went haywire?


 
 Return to top of page · Post #: 15 · Written at 4:59:20 PM on 30 June 2019.
STC830's Gravatar
 Location: NSW
 Member since 10 June 2010
 Member #: 681
 Postcount: 805

As luck would have it, the latest Silicon Chip magazine has an article on a National AKQ Walkabout portable which has valve lineup
1R5 1T4 1S5 3S4. So that should be a help.

I wonder if they toyed with the name Walkman but passed it up for Walkabout..........


 
« Back · 1 · 2 · Next »
 You need to be a member to post comments on this forum.

Sign In

Username:
Password:
 Keep me logged in.
Do not tick box on a computer with public access.